by exchanging his productions for those from the
presses of rival printers living in the same or nearby
towns. The exchange was usually made on the
simple basis of relative numbers of sheets, one book
of 48 leaves (12 sheets of 4 leaves each) being reck-
oned the equivalent of three copies of a book of 16
leaves. The distance between the places where such
exchanges were made rapidly increased, correspond-
ingly enlarging the variety of each bookseller's
stock. This was facilitated by the steady improve-
ment Sn means of transportation — the smoothing
of main highways, the widening of bridle paths into
roads, and the making of lighter carts with smaller
wheels, being among the more significant changes
in northern Europe which went on throughout the
fifteenth century.

Koberger led the movement from exchanges to
sales over a wide area. Starting in 1472, by 1480 he
was doing more business than his own establish-
ment could handle* He employed Rusch to print, or
to get printed, a portion of a monumental Bible
with elaborate Commentary by Nicolas de Lyra,
the whole work making either five or seven volumes,
this depending upon how it was divided for binding.
Rusch in turn had to hire additional type from
Basle* The Basle printer, JOHANN OF AMERBACH,
was just starting on a long and prosperous career,
but already his resources justified him in thinking
of issuing a rival edition of this de Lyra Bible.